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1. Forest regeneration following ungulate removal in a montane Hawaiian wet forest

   https://doi.org/10.1111/rec.13116  

   Hart, Patrick J. ; Ibanez, Thomas ; Uehana, Shea ; Pang‐Ching, Joshua ( February 2020 , Restoration Ecology)

   Most Hawaiian forests lack resiliency following disturbance due to the presence of non‐native and invasive plant and animal species. The montane wet forest within Hakalau Forest National Wildlife Refuge on Hawai'i island has a long history of ungulate disturbance but portions of the refuge were fenced and most ungulates excluded by the early 1990s. We examined patterns of regeneration within two 100 ha study sites in this forest following the removal of ungulates and in the absence of invasive woody tree species to determine, in part, if passive restoration techniques can be successful under these conditions. We characterized growth, mortality, and basal area (BA) changes for approximately 7,100 marked individuals of all native tree species present in two surveys over a 17–18‐year period within two hundred 30 m diameter forest plots. Considerable recruitment within plots of new trees of all species significantly changed size class distributions and erased deficits in small‐sized trees observed during the first survey, particularly for the codominant canopy tree, koa (Acacia koa). Overall, growth of established dominant 'ōhi'a trees (Metrosideros polymorpha) and recruitment of mid‐canopy trees contributed to increases in BA while high levels of mortality for largeA.koatrees contributed to decreased BA. This resulted in a slight increase in BA between the two surveys (+1.9%). This study demonstrates that fencing and ungulate removal may have rescued theA.koapopulation by facilitating the first real pulse in recruitment in over a century, and that passive restoration can be a successful management strategy in this forest.

    

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2. Whitebark pine facilitation at treeline: potential interactions for disruption by an invasive pathogen

   https://doi.org/10.1002/ece3.2198  

   Tomback, Diana F. ; Blakeslee, Sarah C. ; Wagner, Aaron C. ; Wunder, Michael B. ; Resler, Lynn M. ; Pyatt, Jill C. ; Diaz, Soledad ( June 2016 , Ecology and Evolution)

   In stressful environments, facilitation often aids plant establishment, but invasive plant pathogens may potentially disrupt these interactions. In many treeline communities in the northernRockyMountains of theU.S. andCanada,Pinus albicaulis, a stress‐tolerant pine, initiates tree islands at higher frequencies than other conifers – that is, leads to leeward tree establishment more frequently. The facilitation provided by a solitary (isolated)P. albicaulisleading to tree island initiation may be important for different life‐history stages for leeward conifers, but it is not known which life‐history stages are influenced and protection provided. However,P. albicaulismortality from the non‐native pathogenCronartium ribicolapotentially disrupts these facilitative interactions, reducing tree island initiation. In twoRockyMountain eastern slope study areas, we experimentally examined fundamental plant–plant interactions which might facilitate tree island formation: the protection offered byP. albicaulisto leeward seed and seedling life‐history stages, and to leeward krummholz conifers. In the latter case, we simulated mortality fromC. ribicolafor windwardP. albicaulisto determine whether loss ofP. albicaulisfromC. ribicolaimpacts leeward conifers. Relative to other common solitary conifers at treeline, solitaryP. albicaulishad higher abundance. More seeds germinated in leeward rock microsites than in conifer or exposed microsites, but the odds of cotyledon seedling survival during the growing season were highest inP. albicaulismicrosites. Planted seedling survival was low among all microsites examined. Simulating death of windwardP. albicaulisbyC. ribicolareduced shoot growth of leeward trees. Loss ofP. albicaulisto exotic disease may limit facilitation interactions and conifer community development at treeline and potentially impede upward movement as climate warms.

    

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3. Selection for genetics‐based architecture traits in a native cottonwood negatively affects invasive tamarisk in a restoration field trial

   https://doi.org/10.1111/rec.12840  

   Mahoney, Sean M. ; Mike, Jesse B. ; Parker, Jackie M. ; Lassiter, Linda S. ; Whitham, Thomas G. ( July 2018 , Restoration Ecology)

   Climate change and competition from invasive species remain two important challenges in restoration. We examined the hypothesis that non‐native tamarisk (Tamarixspp.) reestablishment after aboveground removal is affected by genetics‐based architecture of native Fremont cottonwood (Populus fremontii) used in restoration. As cottonwood architecture (height, canopy width, number of stems, and trunk diameter) is, in part, determined by genetics, we predicted that trees from different provenances would exhibit different architecture, and mean annual maximum temperature transfer distance from the provenances would interact with the architecture to affect tamarisk. In a common garden in Chevelon, AZ, U.S.A. (elevation 1,496 m), with cottonwoods from provenances spanning its elevation distribution, we measured the performance of both cottonwoods and tamarisk. Several key findings emerged. On average, cottonwoods from higher elevations were (1) two times taller and wider, covered approximately 3.5 times more basal area, and were less shrubby in appearance, by exhibiting four times fewer number of stems than cottonwoods from lower elevations; (2) had 50% fewer tamarisk growing underneath, which were two times shorter and covered 6.5 times less basal area than tamarisk growing underneath cottonwoods of smaller stature; and (3) the number of cottonwood stems did not affect tamarisk growth, possibly because the negative relationship between cottonwood stems and basal area. In combination, these findings argue that cottonwood architecture is affected by local conditions that interact with genetics‐based architecture. These interactions can negatively affect the growth of reinvading tamarisk and enhance restoration success. Our study emphasizes the importance of incorporating genetic and environmental interactions of plants used in restoration.

    

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4. Prolific fruit output by the invasive tree Bellucia pentamera Naudin (Melastomataceae) is enhanced by selective logging disturbance

   https://doi.org/10.1111/btp.12545  

   Dillis, Christopher ; Marshall, Andrew J. ; Webb, Campbell O. ; Grote, Mark N. ( March 2018 , Biotropica)

   Selective logging in tropical rain forests may promote population growth of invasive plants. The ability of invaders to respond, specifically in reproductive traits, to increase in resource abundance may allow them to increase their presence in the seed rain of recipient communities. The invasive pioneer treeBellucia pentamera(Melastomataceae) is currently spreading within Gunung Palung National Park in West Kalimantan, Indonesia. The park has also experienced periods of illegal, small‐scale, selective logging that seem to have facilitated population growth and spread of this invader. We first used fruiting frequency as a proxy for fruit output to make comparisons betweenB. pentameraand the native tree community of over 200 genera. We then constructed two Generalized Linear Autoregressive Moving Average (GLARMA) models using 13 months of phenology data to predict both fruiting frequency and crop size ofB. pentameraunder selective logging versus natural treefall disturbance regimes.Bellucia pentamerafruited at considerably higher frequency than all 200 native genera considered. This invader also responded positively to selective logging with both odds of being in fruit and crop sizes at least doubling in logged plots. Prolific seed output ofB. pentamerais especially problematic within the lottery competition of tropical rain forest gap tree communities, in which prominence in the seed rain is particularly important. Furthermore, the reproductive response ofB. pentamerato selective logging suggests that this harvesting practice may have a considerable role in facilitating this invasion in Southeast Asia.

    

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5. Consequences of biodiversity shift across phylogenetic scales for aspen and willow growth, survival, and herbivory

   https://doi.org/10.1111/jvs.12716  

   Grossman, Jake J. ; Cavender‐Bares, Jeannine ; Bruun, ed., Hans Henrik ( March 2019 , Journal of Vegetation Science)

   It has been established that community biodiversity has consequences for ecosystem function. Yet research assessing these biodiversity–ecosystem function (BEF) relationships usually occurs at only one phylogenetic scale; as such, the dependence ofBEFrelationships on phylogenetic scale has not been characterized. We present a novel framework for considering the consequences of biodiversity across phylogenetic scales, allowing us to ask: Do the consequences of intraspecific and interspecific diversity affect the growth, survival, and leaf herbivory of three temperate tree species?

   Salicaceous tree plantation, Minnesota, northern USA.

   We established an experimental plantation consisting of trees of three species within the willow (Salicaceae) family. Two aspen (Populus tremuloides,P. alba) and one willow (Salix nigra) species were represented by three unique genotypes such that tree neighborhoods varied both in genotype richness (intraspecific diversity) and species richness (interspecific diversity). We assessed the consequences of tree identity and diversity across these two phylogenetic scales for all trees’ aboveground productivity and survival, and for herbivore damage (onP. tremuloides) at the end of the second full growing season of the experiment.

   Diversity at any phylogenetic scale had no effect on the growth and survival ofP. albaorS. nigra. However, intraspecific diversity increased the likelihood ofP. tremuloidessurvival while interspecific diversity reducedP. tremuloidessurvival. Intraspecific diversity also reduced leaf removal and galling herbivory onP. tremuloides, while interspecific diversity had no effect on leaf removal and increased galling herbivory. Neither scale of diversity affected leaf mining.

   Tree diversity within and among populations and species affected plant performance and ecosystem properties differentially, demonstrating thatBEFrelationships shift across phylogenetic scales in a taxon‐specific manner. We call for further experiments that explicitly span these scales by measuring ecosystem and physiological responses to the manipulation of diversity within and among species.

    

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